A neo-pythagorean approach towards an atomic-mass standard

Summary

Avogadro’s constant,N _A, is usually considered an obligatory passage for a new definition of the unit of mass, the kilogram, though the uncertainty with whichN _A is known at present does not allow us to expect either a new definition of the unit or the substitution for the Pt-Ir standard maintained at Sèvres to occur in the near future. The alternative we propose is based on an algorithm, by which the unit of mass can be defined and materialized by a standard represented by a silicon sphere containing a countable number of atoms. To ensure continuity with the present system, the mass of the sphere should differ from the mass of the Pt-Ir standard by less than a few micrograms. The present proposal, too, cannot be expected to become concrete in a short time; on the other hand, by applying the algorithm in question, density measurements are not required and mass differences can be determined by counting the atoms present in individual objects with an uncertainty lower than the present one.